A new strategy for exploiting ion exchange in sequential injection analysis: in-line phytic acid separation/determination in foods as an example.

A novel strategy for exploiting ion exchange in sequential injection systems is proposed. The procedure is based on the selection of a defined volume of a resin suspension, which is introduced and packed in the analytical path, establishing a resin mini-column in the system. The passage of a selected sample volume through the resin mini-column leads to the retention of the analyte, while the sample matrix is discarded. The analyte is eluted during the passage of the eluant/reagent by the packed beads, being the analytical signal monitored (absorbance) in the liquid phase. The beads are then aspirated back to the holding coil and directed to a recovery flask, linked at the selection valve; then the system is ready to begin a new cycle. With the proposed strategy, the main characteristics of the sequential injection system are kept as any new artifact is added to the manifold and system reconfiguration is not required. The feasibility of the approach is demonstrated by the phytic acid determination in food samples. For this specific application, AG1-X8 was selected as ion exchanger, and a solution containing Cl- and Fe(III)-salicylate complex was used as eluant and spectrophotometric reagent.